Mounting table and plasma processing apparatus

ABSTRACT

A mounting table includes a base member, having a rear surface and a front surface facing the rear surface, in which a coolant path is formed, a groove portion having a bottom surface within the base member being annularly formed on the front surface, the base member being divided into a cylindrical inner base member portion positioned at an inner side of the groove portion and an annular outer base member portion positioned at an outer side of the groove portion by the groove portion; an annular focus ring supported by the outer base member portion, the annular focus ring having, at an inner side surface thereof, a protrusion that is protruded radially and inwardly to cover the groove portion; a first heat transfer member provided between the mounting surface and the coolant path; and a second heat transfer member provided between the focus ring and the coolant path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2013-016703 filed on Jan. 31, 2013, and U.S. Provisional ApplicationSer. No. 61/769,367 filed on Feb. 26, 2013, the entire disclosures ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to a mounting tableand a plasma processing apparatus.

BACKGROUND

As a plasma processing apparatus, there has been known an apparatusincluding a mounting table configured to mount thereon a target object(work piece) (for example, a semiconductor wafer, a glass substrate, andthe like) in a processing chamber (see, for example, Patent Document 1).The plasma processing apparatus described in Patent Document 1 includesan electrostatic chuck configured to mount a wafer thereon. Theelectrostatic chuck has a central portion on which a wafer is mounted,and a flange portion formed to surround the central portion. Above theflange portion, an annular focus ring is provided to be apart from anupper surface of the flange portion. That is, there is a gap between alower surface of the focus ring and the upper surface of the flangeportion. Further, it is described that a heater is embedded in the focusring, and a minute space for introducing a cooling gas is formed at thelower surface of the focus ring. The electrostatic chuck is connected toa RF power supply.

Patent Document 1: Specification of U.S. Pat. No. 6,795,292

In microprocessing for manufacturing a semiconductor device or a FPD(Flat Panel Display) using plasma, it is very important to control atemperature and a temperature distribution of a target object as well asa plasma density distribution on the target object. If the temperatureof the target object is not appropriately controlled, uniformity of asurface reaction on the target object and uniformity of processcharacteristics cannot be secured. As a result, a production yield ofsemiconductor devices or display devices is reduced.

In order to control a temperature of a target object, there has beenwidely used a heater manner in which a heating element that generatesheat when an electric current is applied is mounted on a mounting tableand Joule heat generated from the heating element is controlled.Further, there has been widely used a method in which heat of a targetobject is absorbed by forming a coolant path within a mounting table.Furthermore, as described in Patent Document 1, in order to control atemperature of a focus ring, there has been provided a configuration inwhich a heater is embedded in a focus ring and a coolant for absorbingheat is introduced to a lower surface of the focus ring. By using thesetemperature control units, a set temperature of a target object and aset temperature of a focus ring are required to be maintained in anoptimum temperature range for each processing condition of the targetobject.

The importance of the control of a focus ring temperature will bedescribed below. FIG. 6A and FIG. 6B are graphs showing a dependency ofa working shape of a wafer as a target object on a distance from acenter of the wafer (wafer center). FIG. 6A is a graph showing adependency of a hole depth on a distance from the wafer center. Thehorizontal axis represents a distance from the wafer center, and thelongitudinal axis represents a hole depth. FIG. 6B is a graph showing adependency of a hole shape on a distance from the wafer center. Thehorizontal axis represents a distance from the wafer center, and thelongitudinal axis represents top CD. In both FIG. 6A and FIG. 6B, eachtemperature of a focus ring is plotted. As shown in FIG. 6A and FIG. 6B,a temperature of a focus ring greatly affects a hole depth particularlyat a wafer end portion (for example, 145 mm to 147 mm). FIG. 7A and FIG.7B are graphs showing a dependency of an etching rate (E/R) on a waferposition. FIG. 7A is a graph in a case where a temperature of a focusring is not controlled. FIG. 7B is a graph in a case where a temperatureof a focus ring is controlled to be low. In both FIG. 7A and FIG. 7B,X-axis and Y-axis are orthogonal to each other on the wafer, and resultsmeasured along these axes are plotted on the graphs. According to acomparison between FIG. 7A and FIG. 7B, in the case where a temperatureof a focus ring is controlled to be low, an etching rate at the waferend portion (for example, 145 mm to 147 mm) is closer to an etching rateat the wafer center. Thus, uniformity of an etching rate in the entiresurface of the wafer is improved.

As such, in order to obtain uniformity of process accuracy in the entiresurface of the target object, a temperature control unit for a focusring as shown in the plasma processing apparatus described in PatentDocument 1 as well as a temperature control unit for a target objectneeds to be provided. As a conventional mounting table, for example, amounting table depicted in FIG. 8 may be considered. As depicted in FIG.8, a mounting table 200 includes an aluminum base member 30 havingtherein coolant paths 200 e and 200 d, and an electrostatic chuck 60having a wafer mounting surface 60 d and a focus ring mounting surface60 e. The base member 30 serves as a high frequency electrode, and theelectrostatic chuck 60 is made of ceramic or the like and provided onthe aluminum base member 30. The electrostatic chuck 60 has a centralportion 60 g and a flange portion 60 h formed to surround the centralportion 60 g. An upper surface of the central portion 60 g serves as thewafer mounting surface 60 d, and an upper surface of the flange portion60 h serves as the focus ring mounting surface 60 e. Heaters 60 c and 7c are provided under the wafer mounting surface 60 d and the focus ringmounting surface 60 e, for example, within the electrostatic chuck 60,and configured to independently control temperatures of the wafermounting surface 60 d and the focus ring mounting surface 60 e,respectively. In order to control temperatures of the wafer and thefocus ring to be increased, the heaters 60 c and 7 c supply heat to thewafer mounting surface 60 d and the focus ring mounting surface 60 e,respectively. Further, in order to control temperatures of the wafer andthe focus ring to be decreased, heat is transferred and absorbed fromthe wafer mounting surface 60 d and the focus ring mounting surface 60 eto the coolant paths 200 e and 200 d within the aluminum base member 30,i.e. in a vertical direction, respectively.

A temperature control of the mounting table configured as describedabove is verified, and a result of the verification is shown in FIG. 9.FIG. 9 is a graph showing temperatures measured at each distance(radius) from the center of the mounting table, and the horizontal axisrepresents a radius, and the longitudinal axis represents a temperature.In FIG. 9, a radius on the inner side of a radius indicated by a dottedline corresponds to a wafer region on which the wafer is mounted, and aradius on the outer side of the radius indicated by the dotted linecorresponds to a FR region on which the focus ring is mounted. In FIG.9, a heater in the wafer region is turned off, and a heater in the FRregion is turned on. That is, there is provided a measurement result ina case where a wafer temperature is not controlled, but only a focusring temperature is controlled. As shown in FIG. 9, thermal interferenceoccurs in the vicinity of the radius indicated by the dotted line, i.e.between the wafer region and the FR region, and a temperature at a waferend portion is increased. That is, when the wafer mounting surface andthe focus ring mounting surface are formed on the electrostatic chuck,there occurs thermal diffusion from a focus ring side to a wafer side.Heat introduced into the electrostatic chuck flows not only in thevertical direction starting from the electrostatic chuck to the coolantpaths in the aluminum base member but also in a horizontal direction(diametrical direction of the mounting table) within the electrostaticchuck and at a portion above the coolant paths within the aluminum basemember.

For this reason, as described in Patent Document 1, by forming a gapbetween the lower surface of the focus ring and the upper surface of theflange portion of the electrostatic chuck, the focus ring is not indirect contact with the electrostatic chuck. With this configuration,the direct thermal diffusion from the focus ring side to theelectrostatic chuck side may be suppressed. However, if memberssupporting the focus ring and the electrostatic chuck are thermallyconnected to each other, indirect thermal interference may occur unlessa height position of a coolant path is considered. For this reason,there has been demanded a unit capable of independently controlling atemperature of a target object and a temperature of a focus ring.

Further, even if a temperature of the wafer mounting surface and atemperature of the focus ring mounting surface are controlledseparately, there are problems to be solved as follows. Recently, a settemperature of the focus ring has been demanded to be higher than a settemperature of the target object. By way of example, there has beendemanded to generate a temperature difference of about 100° C. or more.However, if a temperature of the heater right under the wafer mountingsurface is controlled to have a temperature difference of about 40° C.or more from a temperature of the heater right under the focus ringmounting surface, the electrostatic chuck made of ceramic may be damageddue to the thermal expansion. FIG. 10 shows a result of verification ofa maximum stress generated at the electrostatic chuck due to atemperature difference. The horizontal axis represents a temperaturedifference, and the longitudinal axis represents a maximum stressgenerated at a measurement position. The square legend (temperaturedifference: 40° C., maximum stress: 388 MPa) shows the case where atemperature of the focus ring is controlled to be lower than atemperature of the target object, and the other legend shows the casewhere a temperature of the focus ring is controlled to be higher than atemperature of the target object. A reference value of a maximum stressat which damage occurs is 190 MPa. As shown in FIG. 10, when atemperature difference is 40° C. or more, a maximum stress exceeds thereference value of 190 MPa. Such damage is likely to occur at a positionwhere a thickness of the electrostatic chuck is changed. By way ofexample, as depicted in FIG. 8, such damage is likely to occur at astep-shaped portion at the boundary between the wafer mounting surface60 d and the focus ring mounting surface 60 e. Further, since a heatercannot be arranged at a portion where the electrostatic chuck is screwedto the aluminum base member, such a temperature difference can be easilygenerated. As a result, damage is likely to occur at such a portion. Byway of example, as depicted in FIG. 8, when the aluminum base member 30is connected to a supporting member 40 with a screw 8 e, the aluminumbase member 30 is screwed with the supporting member 40 by inserting thescrew 8 e into a through hole 60 i formed within the flange portion 60 hof the electrostatic chuck 60, a through hole 30 a (whose inner surfacemay be screw-cut) formed within the aluminum base member 30, and aninsertion through hole 40 a formed within the supporting member 40 andhaving a screw-cut inner surface. In this case, since the through hole60 i is formed within the electrostatic chuck 60, the heater 7 c cannotbe arranged therein. Therefore, a temperature difference can be easilygenerated at a portion where the through hole 60 i is formed. As aresult, damage is likely to occur at this portion.

Further, in the mounting table as described in Patent Document 1, amember constituting the wafer mounting surface is different from amember constituting the focus ring mounting surface. Therefore, it ispossible to reduce an effect of thermal stress deformation caused by thethermal expansion difference. By way of example, it is proposed toseparately prepare an inner ceramic plate configured to mount a waferand an outer ceramic plate configured to annularly surround the innerceramic plate. Further, heating is controlled with a heater embedded ineach of the ceramic plates. Furthermore, an aluminum plate including acoolant path is provided in each of lower layers of the inner and outerceramic plates, and a heat flux is controlled in the vertical direction.

However, in the above-described configuration, a RF power needs to beapplied to each of the separately provided aluminum plates. Otherwise,it is necessary to apply a power to each of the aluminum plates throughdivided power supply lines, each having a matcher, from a single RFpower supply. In order to perform a complicated application sequencesuch as simultaneous application of a RF power in a pulse waveform, orthe like, a configuration of an apparatus becomes complicated.Therefore, it is desirable to apply a power from a single RF powersupply. Further, since a wafer mounting member and a focus ring mountingmember are different in an area and a thickness, the wafer mountingmember and the focus ring mounting member have conductance componentsgreatly different from each other. By way of example, if each of thewafer mounting member and the focus ring mounting member includes aceramic plate, a conductance component greatly varies depending on anarea and a thickness of the corresponding ceramic plate. For thisreason, if a power supply line is divided into a power supply lineconnected to the wafer and a power supply line connected to the focusring, a RF power may not be distributed appropriately. As a result, asheath field generated at a plasma interface may be non-uniform on thesurface of the wafer and the surface of the focus ring. In such case,there is a problem that a desired semiconductor device cannot bemanufactured.

As such, in the present technical field, there have been demanded amounting table and a plasma processing apparatus capable ofindependently controlling the temperature of the target object and thetemperature of the focus ring, generating a great temperature differencebetween the target object and the focus ring, which is limited by thethermal stress deformation, and generating a uniform sheath field on thesurface of the wafer and the surface of the focus ring in a simpleconfiguration.

SUMMARY

In one example embodiment, a mounting table that mounts thereon a targetobject includes a base member, a mounting member, a focus ring, a firstheat transfer member and a second heat transfer member. The base memberhas a rear surface and a front surface facing the rear surface, and acoolant path is formed in the base member. Further, the rear surface isconnected to a power supply member configured to apply a voltage, and agroove portion having a bottom surface within the base member isannularly formed on the front surface when viewed from a directionperpendicular to the front surface. Moreover, the base member is dividedinto a cylindrical inner base member portion positioned at an inner sideof the groove portion and an annular outer base member portionpositioned at an outer side of the groove portion by the groove portion.The mounting member is supported by the inner base member portion andhas a mounting surface on which the target object is mounted. Theannular focus ring is supported by the outer base member portion andarranged to surround the mounting surface when viewed from a directionperpendicular to the mounting surface. Further, the annular focus ringhas, at an inner side surface thereof, a protrusion that is protrudedradially and inwardly to cover the groove portion when viewed from thedirection perpendicular to the mounting surface. The first heat transfermember is provided between the mounting surface and the coolant path.The second heat transfer member is provided between the focus ring andthe coolant path.

In this mounting table, the mounting member is supported by the innerbase member portion, and the focus ring is supported by the outer basemember portion. By the groove portion (space) which separates the innerbase member portion and the outer base member portion, the mountingmember and the focus ring are thermally separated from each other, sothat heat transfer in a horizontal direction (in a diametrical directionof the mounting table) is suppressed. For this reason, it is possible toindependently control a temperature of the target object and atemperature of the focus ring. Further, since the inner base memberportion and the outer base member portion are separated from each otherwith the space, i.e., the groove portion, even if there is a differencein the thermal expansion between the inner base member portion and theouter base member portion and between the mounting member and the focusring, the constituent components are not damaged by the thermal stressdeformation. As a result, it is possible to generate a great temperaturedifference between the target object and the focus ring, which islimited by the thermal stress deformation. Furthermore, since the powersupply member is connected to the rear surface of the base member andthe groove portion includes the bottom surface within the base member,the inner base member portion and the outer base member portion areconnected to each under the groove portion. As such, the inner basemember portion and the outer base member portion are connected to eachother as a RF circuit. Therefore, it is possible to generate a uniformsheath field on a surface of the target object and a surface of thefocus ring in a simple configuration. Moreover, since plasma to beintroduced into the groove portion is blocked by the protrusion formedat the inner side surface of the focus ring, it is possible to suppressdeterioration of the groove portion or abnormal electric discharge atthe groove portion.

The bottom surface of the groove portion may be located at a heightposition equal to a height position of an uppermost end surface amongupper end surfaces of the coolant path, or lower than the heightposition of the uppermost end surface among the upper end surfaces ofthe coolant path. In this case, since heat flux in a horizontaldirection above the coolant path is blocked by the groove portion, it ispossible to independently control the temperature of the target objectand the temperature of the focus ring.

A height position of an upper end surface of the coolant path formedwithin the inner base member portion may be higher than a heightposition of an upper end surface of the coolant path formed within theouter base member portion, and the bottom surface of the groove portionmay be located at a height position equal to the upper end surface ofthe coolant path formed within the inner base member portion or lowerthan the upper end surface of the coolant path formed within the innerbase member portion. Further, a height position of an upper end surfaceof the coolant path formed within the inner base member portion may belower than a height position of an upper end surface of the coolant pathformed within the outer base member portion, and the bottom surface ofthe groove portion may be located at a height position equal to theupper end surface of the coolant path formed within the outer basemember portion or lower than the upper end surface of the coolant pathformed within the outer base member portion.

The mounting member may include therein the first heat transfer member.In this case, heat may be efficiently transferred to the target object.Further, the mounting member may further include therein an electrodeabove the first heat transfer member, and the electrode may beconfigured to electrostatically hold and attract the target object. Assuch, the mounting member may serve as an electrostatic chuck.

The mounting table may further include a spacer member provided betweenthe focus ring and the outer base member portion, and the spacer membermay include therein the second heat transfer member. In this case, heatmay be efficiently transferred to the target object.

The coolant path may be arranged under the mounting member and the focusring. In this case, it is possible to independently control thetemperature of the target object and the temperature of the focus ring.

The mounting table may further include a supporting member, havingthrough holes therein, that supports the rear surface of the basemember; and fixing members to be inserted into the through holes.Further, fastening portions to be fastened with the fixing members maybe formed on the rear surface of the base member, and the supportingmember and the base member may be fixed to each other by fastening thefixing members to the fastening portions while the fixing members areinserted into the through holes of the supporting member. In this case,since the through holes (screw holes) for fixing the base member to thesupporting member are not formed on the front surface of the basemember, it is possible to suppress a region having a remarkabletemperature difference. Therefore, it is possible to reduce thepossibility of damage of constituent components by the thermal stressdeformation, and possible to generate a great temperature differencebetween the target object and the focus ring, which is limited by thethermal stress deformation.

A plasma processing apparatus includes a processing chamber thatpartitions a processing space where plasma is generated; a gas supplyunit configured to supply a processing gas into the processing space; afirst electrode provided in the processing space; and a mounting tableaccommodated in the processing space and configured to mount thereon atarget object. Further, the mounting table includes a base member,having a rear surface and a front surface facing the rear surface, inwhich a coolant path is formed, the rear surface being connected to apower supply member configured to apply a voltage, a groove portionhaving a bottom surface within the base member being annularly formed onthe front surface when viewed from a direction perpendicular to thefront surface, the base member being divided into a cylindrical innerbase member portion positioned at an inner side of the groove portionand an annular outer base member portion positioned at an outer side ofthe groove portion by the groove portion; a mounting member that issupported by the inner base member portion and has a mounting surface onwhich the target object is mounted; an annular focus ring that issupported by the outer base member portion and arranged to surround themounting surface when viewed from a direction perpendicular to themounting surface, the annular focus ring having, at an inner sidesurface thereof, a protrusion that is protruded radially and inwardly tocover the groove portion when viewed from the direction perpendicular tothe mounting surface; a first heat transfer member provided between themounting surface and the coolant path; and a second heat transfer memberprovided between the focus ring and the coolant path.

According to this plasma processing apparatus, the same effects asdescribed above with regard to the mounting table can be obtained.

In accordance with various aspects and example embodiments, it ispossible to provide a mounting table and a plasma processing apparatuscapable of independently controlling a temperature of a target objectand a temperature of a focus ring, generating a great temperaturedifference between the target object and the focus ring, which islimited by thermal stress deformation, and generating a uniform sheathfield on a surface of the target object and a surface of the focus ringin a simple configuration.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent from the following detailed description. The use of the samereference numbers in different figures indicates similar or identicalitems.

FIG. 1 is a schematic cross sectional view illustrating a configurationof a plasma processing apparatus in accordance with an exampleembodiment;

FIG. 2 is a schematic cross sectional view illustrating a mounting tableof the plasma processing apparatus in FIG. 1;

FIG. 3 is a schematic diagram for explaining an operation and effect ofthe mounting table of the plasma processing apparatus in FIG. 1;

FIG. 4 illustrates a modification example of the mounting table of theplasma processing apparatus in accordance with the example embodiment;

FIG. 5 illustrates another modification example of the mounting table ofthe plasma processing apparatus in accordance with the exampleembodiment;

FIGS. 6A and 6B are graphs showing a dependency of a working shape of awafer as a target object on a distance from a wafer center;

FIG. 7A and FIG. 7B are graphs showing a dependency of an etching rate(E/R) on a wafer position;

FIG. 8 is a schematic cross sectional view illustrating a configurationof a conventional mounting table;

FIG. 9 is a graph showing temperatures measured at each distance(radius) from a center of a mounting table; and

FIG. 10 is a graph showing a correlation between a maximum stressgenerated at an electrostatic chuck and a temperature difference.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current example. Still, the examplesdescribed in the detailed description, drawings, and claims are notmeant to be limiting. Other embodiments may be utilized, and otherchanges may be made, without departing from the spirit or scope of thesubject matter presented herein. It will be readily understood that theaspects of the present disclosure, as generally described herein andillustrated in the drawings, may be arranged, substituted, combined,separated, and designed in a wide variety of different configurations,all of which are explicitly contemplated herein. Further, theexpressions “up” and “low” are connected to the situation illustrated,and utilized for convenience in the description.

FIG. 1 is a schematic cross sectional view illustrating a configurationof a plasma processing apparatus in accordance with an exampleembodiment. The plasma processing apparatus includes a processingchamber 1 that is airtightly provided and electrically grounded. Theprocessing chamber 1 has a cylindrical shape and is made of, forexample, aluminum. The processing chamber 1 partitions a processingspace where plasma is generated. Within the processing chamber 1, thereis provided a mounting table 2 configured to horizontally mount thereona semiconductor wafer (hereinafter, simply referred to as “wafer”) Wserving as a target object (work piece). The mounting table 2 includes abase member 3 and an electrostatic chuck 6 (mounting member). The basemember 3 is made of a conductive metal such as aluminum or the like andserves as a lower electrode. The electrostatic chuck 6 is configured toelectrostatically hold and attract the wafer W. The base member 3 issupported by a supporting member 4 formed of an insulator, and thesupporting member 4 is provided at a bottom portion of the processingchamber 1. Further, a focus ring 5 formed of, for example, singlecrystalline silicon is provided on an upper periphery of the base member3 via a spacer member 7.

The base member 3 is connected to a power supply rod 50 (power supplymember). The power supply rod 50 is connected to a first RF power supply10 a via a first matching unit 11 a, and also connected to a second RFpower supply 10 b via a second matching unit 11 b. The first RF powersupply 10 a is used for plasma generation and configured to supply ahigh frequency power having a certain frequency to the base member 3 ofthe mounting table 2. Further, the second RF power supply 10 b is usedfor ion attraction (for bias) and configured to supply a high frequencypower having a certain frequency lower than that of the first RF powersupply 10 a to the base member 3 of the mounting table 2. As such, avoltage can be applied to the mounting table 2.

The electrostatic chuck 6 includes an electrode 6 a between insulators 6b, and the electrode 6 a is connected to a DC power supply 12. Further,when a DC voltage is applied from the DC power supply 12 to theelectrode 6 a, the wafer W is held on and attracted to the electrostaticchuck 6 by a Coulomb force.

Within the electrostatic chuck 6, there are provided heaters 6 c (firstheat transfer member) as heating members. These heaters 6 c areconnected to a heater power supply 14. By way of example, the heaters 6c are annularly extended to surround a center of the mounting table 2.By way of example, the heaters 6 c may include a heater configured toheat a central region and a heater annularly extended to surround anoutside of the central region. In this case, it is possible to control atemperature of the wafer W at each of multiple regions positioned in aradial direction from a center of the wafer W. Further, the spacermember 7 on which the focus ring 5 is mounted is an annular member, andwithin the spacer member 7, a heater 7 c (second heat transfer member)as a heating member is provided. The heater 7 c is connected to theheater power supply 14. A temperature of the focus ring 5 is controlledby the heater 7 c. As such, a temperature of the wafer W and atemperature of the focus ring 5 are controlled independently by thedifferent heaters.

Within the base member 3, a coolant path 2 d is formed, and the coolantpath 2 d is connected to a coolant inlet line 2 b and a coolant outletline 2 c. The mounting table 2 can be controlled to have a presettemperature by circulating an adequate coolant such as cooling water orthe like through the coolant path 2 d. Further, a gas supply line (notillustrated) configured to supply a cold heat transfer gas (backsidegas), such as a helium gas or the like, to a rear surface of the wafer Wmay be provided to pass through the mounting table 2 and the like. Thegas supply line is connected to a non-illustrated gas supply source.With this configuration, the wafer W held and attracted on an uppersurface of the mounting table 2 by the electrostatic chuck 6 can becontrolled to have a preset temperature.

Meanwhile, above the mounting table 2, a shower head 16 serving as anupper electrode is provided to face the mounting table 2 in parallel toeach other. The shower head 16 and the mounting table 2 are configuredto serve as a pair of electrodes (upper electrode and lower electrode).

The shower head 16 is provided on a top wall of the processing chamber1. The shower head 16 includes a main body 16 a and an upper top plate16 b serving as an electrode plate. Further, the shower head 16 issupported on an upper portion of the processing chamber 1 via aninsulating member 95. The main body 16 a is made of a conductivematerial, for example, aluminum having an anodically oxidized surfaceand is configured to support the upper top plate 16 b to be detachablyattached to a lower part thereof.

A gas diffusion space 16 c is formed within the main body 16 a, andmultiple gas through holes 16 d are formed in a bottom portion of themain body 16 a to be located under the gas diffusion space 16 c.Further, gas discharge holes 16 e passing through the upper top plate 16b in a thickness direction thereof are formed in the upper top plate 16b to be communicated to the gas through holes 16 d. With thisconfiguration, a processing gas supplied into the gas diffusion space 16c is dispersed in a shower shape and discharged into the processingchamber 1 through the gas through holes 16 d and the gas discharge holes16 e.

A gas inlet opening 16 g configured to introduce a processing gas intothe gas diffusion space 16 c is formed at the main body 16 a. One end ofa gas supply line 15 a is connected to the gas inlet opening 16 g, and aprocessing gas supply source (gas supply unit) 15 configured to supply aprocessing gas is connected to the other end of the gas supply line 15a. A mass flow controller (MFC) 15 b and an opening/closing valve V2 aresequentially provided from an upstream side at the gas supply line 15 a.Further, a processing gas for plasma etching is supplied into the gasdiffusion space 16 c through the gas supply line 15 a from theprocessing gas supply source 15, and is dispersed in a shower shape anddischarged into the processing chamber 1 through the gas through holes16 d and the gas discharge holes 16 e from the gas diffusion space 16 c.

A variable DC power supply 72 is electrically connected to the showerhead 16 serving as the upper electrode via a low pass filter (LPF) 71.The variable DC power supply 72 is configured to turn on/off powersupply by using an on/off switch 73. A current/voltage of the variableDC power supply 72 and an on/off operation of the on/off switch 73 arecontrolled by a control unit 90 to be explained later. Further, as willbe described later, when plasma is generated in the processing space byapplying a high frequency power from the first RF power supply 10 a andthe second RF power supply 10 b to the mounting table 2, the on/offswitch 73 is turned on by the control unit 90 if necessary and a presetDC voltage is applied to the shower head 16 serving as the upperelectrode.

A cylindrical ground conductor 1 a is provided to be extended from aside wall of the processing chamber 1 to a position higher than a heightposition of the shower head 16. The cylindrical ground conductor 1 aincludes a top wall at an upper portion thereof.

An exhaust opening 81 is formed at a bottom portion of the processingchamber 1, and a first exhaust device 83 is connected to the exhaustopening 81 via an exhaust pipe 82. The first exhaust device 83 has avacuum pump, and an inside of the processing chamber 1 can bedepressurized to a preset vacuum level by operating the vacuum pump.Meanwhile, a loading/unloading opening 84 for the wafer W is formed atthe side wall of the processing chamber 1, and a gate valve 85configured to open and close the loading/unloading opening 84 isprovided at the loading/unloading opening 84.

On an inner side of the processing chamber 1, a deposit shield 86 isprovided along the inner wall surface. The deposit shield 86 isconfigured to suppress an etching by-product (deposit) from beingdeposited on the processing chamber 1. At the deposit shield 86, aconductive member (GND block) 89 is provided at substantially the sameheight position as that of the wafer W, so that an abnormal electricdischarge is suppressed. Further, at a lower end portion of the depositshield 86, there is provided a deposit shield 87 extended along themounting table 2. The deposit shields 86 and 87 are detachably attached.

An overall operation of the plasma processing apparatus configured asdescribed above is controlled by the control unit 90. The control unit90 includes a process controller 91 that includes a CPU and controlseach part of the plasma processing apparatus, a user interface 92, and astorage unit 93.

The user interface 92 includes a keyboard by which a process managerinputs a command to manage the plasma processing apparatus, and adisplay that visibly displays an operation status of the plasmaprocessing apparatus.

The storage unit 93 stores a recipe of a control program (software) orprocessing condition data for enabling various processes executed in theplasma processing apparatus to be performed under the control of theprocess controller 91. Then, if necessary, a desired process isperformed in the plasma processing apparatus under the control of theprocess controller 91 by retrieving a certain recipe from the storageunit 93 in response to an instruction or the like from the userinterface 92 and executing the recipe in the process controller 91.Further, the recipe of the control program, the processing conditiondata, or the like may be stored in a computer-readable storage medium(for example, a hard disc, a CD, a flexible disc, a semiconductormemory, or the like), or may be transmitted at any time through, forexample, a dedicated line from another device and used online.

Hereinafter, referring to FIG. 2, a configuration of main components ofthe mounting table 2 will be explained. FIG. 2 is a schematic crosssectional view illustrating the mounting table 2 of the plasmaprocessing apparatus in FIG. 1.

For example, the base member 3 has a substantially cylindrical shape,and includes a rear surface 3 c and a front surface (upper surface 3 dand upper surface 3 e) facing the rear surface 3 c. The power supply rod50 is connected to the rear surface 3 c of the base member 3 along anaxis line Z of the base member 3. Further, at the rear surface 3 c ofthe base member 3, there are formed through holes 3 f to 3 i used inassembling the supporting member 4. Details of the assembly of the basemember 3 and the supporting member 4 will be explained later. Althoughfour through holes are illustrated in FIG. 2, the through holes may beformed at equivalent intervals in an annular direction or in acircumferential direction to surround the axis line Z of the base member3. Further, in FIG. 2, the through holes 3 f and 3 i are annularlyarranged along an outer periphery of the rear surface 3 c, and thethrough holes 3 g and 3 h are annularly arranged at an inside of thethrough holes 3 f and 3 i. Herein, the through holes arranged doubly andannularly have been explained, but the arrangement of the through holescan be set appropriately. By way of example, the through holes may beformed to be arranged at only an outer periphery of the base member 3.

A groove portion 13 is annularly formed on the front surface of the basemember to surround the axis line Z of the base member 3. That is, thegroove portion 13 is formed in an annular manner when viewed from adirection perpendicular to the front surface of the base member 3.Further, the groove portion 13 may be continuously or intermittentlyformed in an annular manner. By the groove portion 13, an upper portionof the base member 3 is divided into a circular inner base memberportion 3 a and an annular outer base member portion 3 b when viewedfrom the direction perpendicular to the front surface of the base member3. An axis line of the cylindrical inner base member portion 3 a isidentical with the axis line Z of the base member 3. Further, the outerbase member portion 3 b is formed to surround the axis line Z of thebase member 3, i.e. the axis line of the inner base member portion 3 a.The inner base member portion 3 a includes the circular upper surface 3d that supports the electrostatic chuck 6. The outer base member portion3 b includes the annular upper surface 3 e that supports the focus ring5. As such, the front surface of the base member 3 is divided into thecircular upper surface 3 d and the annular upper surface 3 e by thegroove portion 13.

Heights of the upper surface 3 d and the upper surface 3 e areappropriately controlled depending on a thickness of the wafer W and athickness of the focus ring 5, or a thickness or a property of amaterial interposed between the wafer W and the inner base memberportion 3 a and a thickness or a property of a material interposedbetween the focus ring 5 and the outer base member portion 3 b such thatheat transfer or a RF power to the wafer W becomes equivalent to heattransfer or a RF power to the focus ring 5. That is, although FIG. 2illustrates an example where the height of the upper surface 3 d is notequivalent to a height of the upper surface 3 e, the both heights of theupper surface 3 d and the upper surface 3 e may be the same.

The coolant path 2 d formed within the base member 3 (see FIG. 2)includes an inner coolant path 2 e arranged at an inner position of thebase member 3 than the groove portion 13 and an outer coolant path 2 farranged at an outer position of the base member 3 than the grooveportion 13. The inner coolant path 2 e is formed under the upper surface3 d of the inner base member portion 3 a. The outer coolant path 2 f isformed under the upper surface 3 e of the outer base member portion 3 b.That is, the inner coolant path 2 e is positioned under the wafer W andconfigured to absorb heat of the wafer W, and the outer coolant path 2 fis positioned under the focus ring 5 and configured to absorb heat ofthe focus ring 5. Further, the inner coolant path 2 e and the outercoolant path 2 f may be connected to different cooling units, so thatcoolants having different temperatures may be flown, respectively.

The groove portion 13 includes a bottom surface 13 a within the basemember 3. That is, the inner base member portion 3 a and the outer basemember portion 3 b are connected to each other under the groove portion13. With reference to a height position P of the rear surface 3 c of thebase member 3, a height position B of the bottom surface 13 a is equalto or lower than a height of the uppermost end surface among upper endsurfaces of the coolant paths 2 e and 2 f. FIG. 2 illustrates an examplewhere the upper end surfaces of the coolant paths 2 e and 2 f have thesame height H1. For this reason, the height position B of the bottomsurface 13 a of the groove portion 13 may be equal to or lower than theheight H1. As such, since the groove portion 13 is formed at least up tothe upper end surfaces of the coolant paths 2 e and 2 f, a space isformed above the coolant paths 2 e and 2 f to interrupt physicalcontinuity. Therefore, it is possible to suppress heat from beingtransferred in a horizontal direction within the base member 3. Sincethe space is in a vacuum state during a plasma process, it is possibleto provide heat insulation by vacuum.

The electrostatic chuck 6 is provided on the upper surface 3 d of theinner base member portion 3 a via an adhesive 9 b. The electrostaticchuck 6 has a circular plate shape and is arranged to have the same axisline as the axis line Z of the base member 3. At an upper end of theelectrostatic chuck 6, there is formed a mounting surface 6 d configuredto mount thereon the wafer W. The mounting surface 6 d has a circularshape and is brought into contact with the rear surface of the wafer Wto support the circular plate-shaped wafer W. Further, at a lower end ofthe electrostatic chuck 6, there is formed a flange portion 6 eprotruding radially and outwardly from the electrostatic chuck 6. Thatis, an outer diameter of the electrostatic chuck 6 varies depending on aposition of a side surface thereof. Further, the electrostatic chuck 6includes the electrode 6 a and the heaters 6 c between the insulators 6b. In FIG. 2, the heaters 6 c are provided under the electrode 6 a.Heating of the mounting surface 6 d is controlled by the heaters 6 c.Further, the heaters 6 c may not be provided within the electrostaticchuck 6. By way of example, the heaters 6 c may be attached to a rearsurface of the electrostatic chuck 6 with the adhesive 9 b or may beprovided at a portion between the mounting surface 6 d and the coolantpath 2 e.

By way of example, the focus ring 5 is supported by the outer basemember portion 3 b via the spacer member 7. The focus ring 5 is acircular ring-shaped member and arranged to have the same axis line asthe axis line Z of the base member 3. At the inner side surface of thefocus ring 5, there is formed a protrusion 5 a protruding radially andinwardly from the focus ring 5. That is, an inner diameter of the focusring 5 varies depending on a position of an inner side surface thereof.By way of example, an inner diameter of a portion of the focus ring 5where the protrusion 5 a is not formed is greater than an outer diameterof the wafer W and an outer diameter of the flange portion 6 e of theelectrostatic chuck 6. Meanwhile, an inner diameter of a portion of thefocus ring 5 where the protrusion 5 a is formed is smaller than theouter diameter of the flange portion 6 e of the electrostatic chuck 6and greater than an outer diameter of a portion of the electrostaticchuck 6 where the flange portion 6 e is not formed.

The focus ring 5 is arranged on an upper surface of the spacer member 7such that the protrusion 5 a is spaced from an upper surface of theflange portion 6 e of the electrostatic chuck 6 and also spaced from aside surface of the electrostatic chuck 6. That is, there is formed agap between a lower surface of the protrusion 5 a of the focus ring 5and the upper surface of the flange portion 6 e of the electrostaticchuck 6, and between a side surface of the protrusion 5 a of the focusring 5 and the side surface of the electrostatic chuck 6 where theflange portion 6 e is not formed. Further, the protrusion 5 a of thefocus ring 5 is positioned above the groove portion 13. That is, whenviewed from a direction perpendicular to the mounting surface 6 d, theprotrusion 5 a is positioned to be overlapped with the groove portion 13and covers the groove portion 13. Thus, it is possible to suppressplasma from being introduced into the groove portion 13.

The spacer member 7 is an annular member and arranged to have the sameaxis line as the axis line Z of the base member 3. The spacer member 7is provided on the upper surface 3 e of the outer base member portion 3b via an adhesive 9 a. The spacer member 7 is made of an insulator suchas ceramic or the like. An upper surface 7 d of the spacer member 7 isbrought into contact with the focus ring 5 to support the focus ring 5.The focus ring 5 is supported by the spacer member 7 and arranged tosurround the wafer W (the mounting surface 6 d of the electrostaticchuck 6). The spacer member 7 includes therein the heater 7 c. Heatingof the upper surface 7 d (a mounting surface of the focus ring 5) of thespacer member 7 is controlled by the heater 7 c. Further, the heater 7 cmay not be provided within the spacer member 7. By way of example, theheater 7 c may be attached to a rear surface of the spacer member 7 withthe adhesive 9 a or may be provided at a portion between the focus ring5 and the coolant path 2 f.

The base member 3 is supported by the cylindrical supporting member 4made of an insulator such as ceramic or the like. The supporting member4 includes through holes 4 a to 4 d through which screws are inserted tobe passed through from a rear surface of the supporting member 4. Thethrough holes 4 a to 4 d are formed to correspond to the through holes 3f to 3 i of the base member 3. At an inner side of the through holes 3 fto 3 i of the base member 3, there are formed screw portions (fasteningportions) to be fastened with screws 8 a to 8 d (fixing members).Further, at the through holes 4 a to 4 d, there may be formed screwportions (fastening portions) to be fastened with the screws 8 a to 8 d(fixing members). The base member 3 and the supporting member 4 arearranged such that the through holes 4 a to 4 d of the supporting memberare overlapped with the through holes 3 f to 3 i of the base member 3,and the base member 3 and the supporting member 4 are screw-fixed byinserting the screws 8 a to 8 d to be passed through from the rearsurface of the supporting member 4. As a result, the base member 3 andthe supporting member 4 are connected and fixed to each other.

Hereinafter, referring to FIG. 3, an operation and effect of themounting table 2 will be explained. FIG. 3 is a schematic diagram forexplaining an operation and effect of the mounting table 2. As depictedin FIG. 3, in the mounting table 2, the electrostatic chuck 6 issupported by the inner base member portion 3 a, and the focus ring 5 issupported by the outer base member portion 3 b. By the groove portion 13(space) which separates the inner base member portion 3 a and the outerbase member portion 3 b, the electrostatic chuck 6 and the focus ring 5are thermally separated from each other. For this reason, heat transferin a horizontal direction (in a diametrical direction of the mountingtable 2) indicated by an arrow D is suppressed, and heat of the wafer Wis transferred from the electrostatic chuck 6 to the inner coolant path2 e, i.e. in a vertical direction, as indicated by an arrow E. Likewise,heat of the focus ring 5 is transferred to the outer coolant path 2 f,i.e. in a vertical direction, as indicated by an arrow A. As such, heattransfer between the members positioned above the bottom surface 13 a ofthe groove portion 13 is suppressed. By way of example, by forming thespace, the wafer W, the electrostatic chuck 6, the adhesive 9 b, and aportion of the inner base member portion 3 a between the upper surface 3d of the inner base member portion 3 a and the an upper end surface ofthe inner coolant path 2 e are separated from the focus ring 5, thespacer member 7, the adhesive 9 a, and a portion of the outer basemember portion 3 b between the upper surface 3 e of the outer basemember portion 3 b and the upper end surface of the outer coolant path 2f. As a result, heat transfer therebetween is suppressed. For thisreason, it is possible to independently control the temperature of thewafer W and the temperature of the focus ring 5.

Further, since the inner base member portion 3 a and the outer basemember portion 3 b are separated from each other with the space, i.e.,the groove portion 13, even if there is a difference in thermalexpansion between the inner base member portion 3 a and the outer basemember portion 3 b, and between the electrostatic chuck 6 and the focusring 5, the constituent components are not damaged by thermal stressdeformation. Furthermore, the screws 8 c and 8 d are inserted from aside of the rear surface 3 c of the base member 3. Thus, since thethrough holes (or screw holes) for fixing the base member 3 to thesupporting member 4 are not formed on the front surface of the basemember 3, the heaters 6 c and 7 c can be arranged uniformly. As aresult, it is possible to suppress a region having a remarkabletemperature difference. Therefore, it is possible to reduce thepossibility of damage of the constituent components by the thermalstress deformation, and possible to generate a great temperaturedifference between the wafer W and the focus ring 5, which is limited bythe thermal stress deformation. As such, the groove portion 13 has notonly a function of insulating the heat transfer, but also a function ofabsorbing the thermal stress deformation.

Furthermore, since the power supply rod 50 is connected to the rearsurface 3 c of the base member 3 and the groove portion 13 includes thebottom surface 13 a within the base member 3, the inner base memberportion 3 a and the outer base member portion 3 b are connected to eachother under the groove portion 13 as indicated by an arrow C. As such,the inner base member portion 3 a and the outer base member portion 3 bare connected to each other as a RF circuit. Therefore, it is possibleto generate a uniform sheath field on a surface of the wafer W and asurface of the focus ring 5 in a simple configuration.

Moreover, since plasma to be introduced into the groove portion 13 isblocked by the protrusion 5 a formed at the inner side surface of thefocus ring 5, it is possible to suppress deterioration of the grooveportion or abnormal electric discharge at the groove portion 13.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

By way of example, as depicted in FIG. 4, a height H2 of the upper endsurface of the inner coolant path 2 e within the base member 3 may behigher than a height H3 of the upper end surface of the outer coolantpath 2 f. In this case, the height B of the bottom surface 13 a of thegroove portion 13 may be equal to or lower than the height H2 of theupper end surface of the coolant path 2 e at the uppermost end surfaceamong the upper end surfaces of the coolant paths 2 e and 2 f. Further,by way of example, as depicted in FIG. 5, the height H2 of the upper endsurface of the inner coolant path 2 e within the base member 3 may belower than the height H3 of the upper end surface of the outer coolantpath 2 f. In this case, the height B of the bottom surface 13 a of thegroove portion 13 may be equal to or lower than the height H3 of theupper end surface of the coolant path 2 f at the uppermost end surfaceamong the upper end surfaces of the coolant paths 2 e and 2 f. As such,the bottom surface 13 a of the groove portion 13 is located at a heightposition cutting off a heat flow path that is formed in the aluminumbase member portion or the like above the outer coolant path 2 f and theinner coolant path 2 e in a horizontal direction.

Further, although the base member 3 is described to be formed as onesingle body in the above example embodiments, separate bodies may becombined to serve as the base member 3. By way of example, the outerbase member portion 3 b may be a separate body. If the outer base memberportion 3 b is a separate body, a surface treatment such as a thermalspraying treatment can be easily performed on the inside of the grooveportion 13.

Furthermore, the plasma processing apparatus may use plasma generatedwith microwave.

We claim:
 1. A mounting table that mounts thereon a target object, comprising: a base member having a rear surface and a front surface facing the rear surface; a coolant path formed within the base member; a groove portion formed within the base member, the groove portion having a bottom surface and having an annular shape when viewed from a direction perpendicular to the front surface, the groove portion dividing the base member into a cylindrical inner base member portion positioned at an inner side of the groove portion and an annular outer base member portion positioned at an outer side of the groove portion, a rear surface of the cylindrical inner base member portion being connected to a power supply member configured to apply a voltage; a mounting member supported by the inner base member portion and having a mounting surface on which the target object is mounted; a focus ring; a focus ring support member supported by the outer base member portion and arranged to support the focus ring; a first heater provided between the mounting surface and the coolant path; a second heater provided on or in the focus ring support member; and a RF power supply connected to the power supply member, wherein the cylindrical inner base member portion and the annular outer base member portion are connected to each other under the groove portion, such that the cylindrical inner base member portion and the annular outer base member portion are formed as an integral body, the base member is made of a conductive metal, such that the cylindrical inner base member portion and the annular outer base member portion are electrically connected to each other as a RF circuit, the groove portion and the coolant path are separated from each other within the base member so as to suppress heat from the second heater from being transferred toward the cylindrical inner base member portion within the base member, the bottom surface of the groove portion is formed at a height position equal to or lower than a height position of an uppermost end surface among upper end surfaces of the coolant path such that a space is formed above the uppermost end surface of the coolant path to suppress heat from being transferred in a horizontal direction within the base member, the coolant path includes an inner coolant path arranged at the cylindrical inner base member portion and an outer coolant path arranged at the annular outer base member portion, and an upper end surface of the outer coolant path is positioned below a surface of the annular outer base member portion.
 2. The mounting table of claim 1, wherein a height position of an upper end surface of the coolant path formed within the inner base member portion is higher than a height position of an upper end surface of the coolant path formed within the outer base member portion, and the bottom surface of the groove portion is located at a height position equal to the upper end surface of the coolant path formed within the inner base member portion or lower than the upper end surface of the coolant path formed within the inner base member portion.
 3. The mounting table of claim 1, wherein a height position of an upper end surface of the coolant path formed within the inner base member portion is lower than a height position of an upper end surface of the coolant path formed within the outer base member portion, and the bottom surface of the groove portion is located at a height position equal to the upper end surface of the coolant path formed within the outer base member portion or lower than the upper end surface of the coolant path formed within the outer base member portion.
 4. The mounting table of claim 1, wherein the mounting member includes therein the first heater.
 5. The mounting table of claim 4, wherein the mounting member further includes therein an electrode above the first heater, and the electrode is configured to electrostatically hold and attract the target object.
 6. The mounting table of claim 1, wherein the coolant path is arranged under the mounting member and the focus ring.
 7. The mounting table of claim 1, further comprising: a supporting member, having through holes therein, that supports the rear surface of the base member; and fixing members to be inserted into the through holes, wherein fastening portions to be fastened with the fixing members are formed on the rear surface of the base member, and the supporting member and the base member are fixed to each other by fastening the fixing members to the fastening portions while the fixing members are inserted into the through holes of the supporting member.
 8. The mounting table of claim 7, wherein the fastening portions and the through holes are respectively provided on the inner base member portion and the outer base member portion, and the inner base member portion and the outer base member portion are fixed to the supporting member by the fixing members.
 9. The mounting table of claim 7, wherein the supporting member is formed of an insulator.
 10. The mounting table of claim 1, wherein the mounting member has a flange portion protruded radially and outwardly at a lower part of the mounting member, a protrusion of the focus ring is extended to cover an upper surface of the flange portion of the mounting member, and a gap is formed between a lower surface of the protrusion of the focus ring and the upper surface of the flange portion, and the gap is extended to the groove portion.
 11. The mounting table of claim 1, wherein the groove portion is continuously formed within the base member.
 12. The mounting table of claim 11, wherein the protrusion of the focus ring is not in contact with the cylindrical inner base member portion.
 13. The mounting table of claim 1, wherein a bottom surface of the groove portion is located at a height position equal to a lowermost end surface among lower end surfaces of the coolant path or lower than the lowermost end surface of the coolant path.
 14. The mounting table of claim 1, wherein the inner coolant path and the outer coolant path are respectively connected to different cooling units.
 15. A plasma processing apparatus comprising: a processing chamber that partitions a processing space where plasma is generated; a gas supply unit configured to supply a processing gas into the processing space; a first electrode provided in the processing space; and a mounting table accommodated in the processing space and configured to mount thereon a target object, wherein the mounting table comprises: a base member having a rear surface and a front surface facing the rear surface, a coolant path formed within the base member, a groove portion formed within the base member, the groove portion having a bottom surface and having an annular shape when viewed from a direction perpendicular to the front surface, the groove portion dividing the base member into a cylindrical inner base member portion positioned at an inner side of the groove portion and an annular outer base member portion positioned at an outer side of the groove portion, a rear surface of the cylindrical inner base member portion being connected to a power supply member configured to apply a voltage; a mounting member supported by the inner base member portion and having a mounting surface on which the target object is mounted; a focus ring; a focus ring support member supported by the outer base member portion and arranged to support the focus ring; a first heater provided between the mounting surface and the coolant path; a heater provided on or in the focus ring support member; and a RF power supply connected to the power supply member, wherein the cylindrical inner base member portion and the annular outer base member portion are connected to each other under the groove portion, such that the cylindrical inner base member portion and the annular outer base member portion are formed as an integral body, the base member is made of a conductive metal, such that the cylindrical inner base member portion and the annular outer base member portion are electrically connected to each other as a RF circuit, the groove portion and the coolant path are separated from each other within the base member so as to suppress heat from the second heater from being transferred toward the cylindrical inner base member portion within the base member, the bottom surface of the groove portion is formed at a height position equal to or lower than a height position of an uppermost end surface among upper end surfaces of the coolant path such that a space is formed above the uppermost end surface of the coolant path to suppress heat from being transferred in a horizontal direction within the base member, the coolant path includes an inner coolant path arranged at the cylindrical inner base member portion and an outer coolant path arranged at the annular outer base member portion, and an upper end surface of the outer coolant path is positioned below a surface of the annular outer base member portion.
 16. The plasma processing apparatus of claim 15, wherein the mounting member has a flange portion protruded radially and outwardly at a lower part of the mounting member, a protrusion of the focus ring is extended to cover an upper surface of the flange portion of the mounting member, and a gap is formed between a lower surface of the protrusion of the focus ring and the upper surface of the flange portion, and the gap is extended to the groove portion.
 17. The plasma processing apparatus of claim 15, wherein the groove portion is continuously formed within the base member.
 18. The plasma processing apparatus of claim 17, wherein the protrusion of the focus ring is not in contact with the cylindrical inner base member portion.
 19. The mounting table of claim 15, wherein the inner coolant path and the outer coolant path are respectively connected to different cooling units. 